Messages in this thread | | | Date | Mon, 7 Aug 2017 15:01:39 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: correct modules range of kernel virtual memory layout |
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On Mon, Aug 07, 2017 at 02:18:00PM +0100, Ard Biesheuvel wrote: > On 7 August 2017 at 14:16, Will Deacon <will.deacon@arm.com> wrote: > > On Mon, Aug 07, 2017 at 07:04:46PM +0800, Miles Chen wrote: > >> The commit f80fb3a3d508 ("arm64: add support for kernel ASLR") > >> moved module virtual address to > >> [module_alloc_base, module_alloc_base + MODULES_VSIZE). > >> > >> Display module information of the virtual kernel > >> memory layout by using module_alloc_base. > >> > >> testing output: > >> 1) Current implementation: > >> Virtual kernel memory layout: > >> modules : 0xffffff8000000000 - 0xffffff8008000000 ( 128 MB) > >> 2) this patch + KASLR: > >> Virtual kernel memory layout: > >> modules : 0xffffff8000560000 - 0xffffff8008560000 ( 128 MB) > >> 3) this patch + KASLR and a dummy seed: > >> Virtual kernel memory layout: > >> modules : 0xffffffa7df637000 - 0xffffffa7e7637000 ( 128 MB) > >> > >> Signed-off-by: Miles Chen <miles.chen@mediatek.com> > >> --- > >> arch/arm64/mm/init.c | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > > > > Does this mean the modules code in our pt dumper is busted > > (arch/arm64/mm/dump.c)? Also, what about KASAN, which uses these addresses > > too (in kasan_init)? Should we just remove MODULES_VADDR and MODULES_END > > altogether? > > > > I don't think we need this patch. The 'module' line simply prints the > VA region that is reserved for modules. The fact that we end up > putting them elsewhere when running randomized does not necessarily > mean this line should reflect that.
I was more concerned by other users of MODULES_VADDR tbh, although I see now that we don't randomize the module region if kasan is enabled. Still, the kcore code adds the modules region as a separate area (distinct from vmalloc) if MODULES_VADDR is defined, the page table dumping code uses MODULES_VADDR to identify the module region and I think we'll get false positives from is_vmalloc_or_module_addr, which again uses the static region.
So, given that MODULES_VADDR never points at the module area, can't we get rid of it?
Will
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